Recently, attention is being given to an artificial tissue which can function in a living body instead of an original tissue of the living body, and development of such an artificial tissue is proceeding.
For example, Patent Literatures 1 and 2 disclose techniques in which a connective tissue is extracted by removing cells and the like from various kinds of tissues derived from an animal that can be transplanted, and the connective tissue thus extracted is used as an artificial tissue.
A variety of the artificial tissue is wide and, for example, development of artificial tissues is proceeding which can serve as soft tissues (e.g., a blood vessel, a heart valve, a cornea, an amnion, a dura mater, and the like), hard tissues (e.g., a bone, a cartilage, a tooth, and the like), or organs (e.g., a heart, a kidney, a liver, a pancreas, a brain, and the like).
Among tissues that exist in a living body, a blood vessel is a tissue which includes a large number of variations in terms of thickness, length, bifurcation, and the like. Moreover, the blood vessel needs to have high strength because (i) the blood vessel is exposed to a severe environment, i.e., is constantly subjected to pressure by a blood flow and (ii) large force is applied to the blood vessel in surgery such as suture.
In recent years, as the number of patients suffering from circulatory system diseases increases, demands for artificial blood vessels increase. In order to meet such demands, various artificial blood vessels have been developed and used.
For example, artificial blood vessels made of synthetic polymers such as ePTFE and Dacron (Registered Trademark) have been developed and used. The artificial blood vessels made of such synthetic polymers effectively function in a case where a cross section of its lumen is large (in other words, in a case of having a medium diameter or a large diameter), and approximately 700,000 pieces of such artificial blood vessels are used per year.